1. Field of the Invention
The current invention relates to position tracking and machine control systems, and, more specifically, to a combination of laser systems and radio positioning systems configured to complement each other in order to optimize the tracking and machine control capabilities of prior art systems.
2. Discussion of the Prior Art
In recent times there have been advances in the area of radio ranging or pseudolite systems. A pseudolite is a ground based radio transmitter that works in the GPS band and transmits signals similar to the GPS system. Because of limitations on using the L band for non-military purposes a new form of “pseudolite” is being developed that uses alternative frequencies such as the 2.4 GHz license free band.
In recent times there have been also advances in rotating laser systems including plane lasers and fan laser systems. Plane lasers provide a reference plane of light. Fan lasers provide one or more planes of light that are rotated about an axis, from which a difference in elevation can be derived. The common technique for deriving the difference in elevation is by determining the difference in time between detection of two or more fan beams. These systems, such as the Trimble LaserStation and Topcon LaserZone systems provide accurate differences in elevation.
However, an inherent weakness in the pseudolite system is the vertical accuracy because it is difficult to position a number of pseudolites to creates a geometric relationship that is mathematically strong in the vertical, due to the fact that the ground based transmitters are commonly located at similar (+/−500 m) elevation.
In addition, an inherent weakness in laser systems is either their inability to provide horizontal position, or limitations on the range over which they can provide horizontal position.